1. Field
The present invention relates to medical instrument technologies, and particularly, to a microscopic image detecting instrument and automatic focusing method therefor.
2. Background
Currently, a microscopic imaging system of a well-known urine analyzer has a fixed-focus. The microscopic imaging system starts to focus from a fixed optical coupling reset position and then moves the objective lens of a microscope to a focal plane of the objective lens by advancing a stepping motor at predetermined steps. A sharpness of the image depends on accuracy of mechanical motion and a non-deformable structure of the microscopic imaging system.
However, an object stage of the microscopic imaging system may go through some gaps or backlashes during a movement due to factors such as machining tolerances, assembly tolerances, transport, and shaking. These factors compromise a positional accuracy of the object stage and change an object distance of the microscopic imaging system. A thermal deformation of the microscopic imaging system caused by ambient temperature changes also leads to a drift and change of the object distance. Therefore, the image may become blurred or unstable because distance between the objective lens and a testing pool is changed during switches of the objective lens and movement of the object stage. A high-quality image is very important to recognition and analysis of digital images. The user usually has to manually focus in order to get the high-quality image, which increases difficulty of use and fails to meet demands of a fully automatic system.
What is needed, therefore, is a microscopic image detecting instrument and automatic focusing method for using the same.